Development of l-Tyrosine-Based Enzyme-Responsive Amphiphilic Poly(ester-urethane) Nanocarriers for Multiple Drug Delivery to Cancer Cells

Size- and Shape-controlled Biodegradable Polymer Brushes Based on l-Amino Acid for Intracellular Drug Delivery and Deep-Tissue Penetration

We report size- and shape-controlled polymer brushes based on l-amino acid bioresource and study the role of polymer topology on the enzymatic biodegradation and deep-tissue penetration under in vitro and in vivo. For this purpose, l-tyrosine-based propargyl-functionalized monomer is tailor-made and polymerized via solvent-free melt polycondensation strategy to yield hydrophobic and clickable biodegradable poly(ester-urethane)s. Postpolymerization click chemistry strategy is applied to make well-defined amphiphilic one-dimensional rodlike and three-dimensional spherical polymer brushes by merely varying the lengths of PEG-azides in the reaction. These core-shell polymer brushes are found to be nontoxic and nonhemolytic and capable of loading clinical anticancer drug doxorubicin and deep-tissue penetrable near-infrared biomarker IR-780. In vitro enzymatic drug-release kinetics and lysotracker-assisted real-time live-cell confocal bioimaging revealed that the rodlike polymer brush is superior than its spherical counterparts for faster cellular uptake and enzymatic biodegradation at the endolysosomal compartments to release DOX at the nucleus. Further, in vivo live-animal bioimaging by IVIS technique established that the IR-780-loaded rodlike polymer brush exhibited efficient deep-tissue penetration ability and emphasized the importance of polymer brush topology control for biological activity. Polymer brushes exhibit good stability in the blood plasma for more than 72 h, they predominately accumulate in the digestive organs like liver and kidney, and they are less toxic to heart and brain tissues. IVIS imaging of cryotome tissue slices of organs confirmed the deep-penetrating ability of the polymer brushes. The present investigation opens opportunity for bioderived and biodegradable polymer brushes as next-generation smart drug-delivery scaffolds.

A novel nanoparticle fluorescent probe based on a water-soluble conjugated polymer for real-time monitoring of ATP fluctuation and configuration of the Golgi apparatus during the inhibition of glycolysis

BACKGROUND

Adenosine 5'-triphosphate (ATP) plays an important role in cell metabolism and has been regarded as an indicator of cell survival and damage. Golgi apparatus participates in the signal transduction processes of substance transport, ion homeostasis and stress when extracellular substances enter cells. Till now, there is no fluorescent probe for monitoring Golgi ATP level fluctuation and visualizing the configuration change of the Golgi apparatus during the inhibition of glycolysis.

RESULTS

Herein, we report the synthesis of a novel water-soluble cationic polythiophene derivative (PEMTEA) that can be employed as a fluorescent sensor for measuring ATP in the Golgi apparatus. PEMTEA self-assembles into PT-NP nanoparticles in aqueous solution with a diameter of approximately 2 nm. PT-NP displays high sensitivity and superb selectivity towards ATP with a detection limit of 90 nM and a linear detection range from 0 to 3.0 μM. The nanoparticles show low toxicity to HepG2 cells and good photostability in the Golgi apparatus. With the stimulation of Ca2+, PT-NP was practically applied to real-time monitor of endogenous ATP levels in the Golgi apparatus through fluorescence microscopy. Finally, we studied the relationship between the concentration of ATP and configuration of the Golgi apparatus during the inhibition of glycolysis using PT-NP.

SIGNIFICANCE

We have demonstrated that PT-NP can not only indicate the fluctuation and distribution of ATP in the Golgi apparatus, but also give the information of the configuration change of the Golgi apparatus at the single-cell level during the inhibition of glycolysis.

Tumor acidity-induced surface charge modulation in covalent nanonetworks for activated cellular uptake: targeted delivery of anticancer drugs and selective cancer cell death

A β-thioester and tertiary amine based covalently cross-linked nanoassembly coined as a nanonetwork (NN) endowed with dual pH responsive features (tumor acidity induced surface charge modulation and endosomal pH triggered controlled degradation) has been designed and synthesized for stable sequestration and sustained release of drug molecules in response to endosomal pH. An amphiphile integrated with tertiary amine and acrylate (ATA) functionalities was synthesized to fabricate the nanonetwork. This amphiphile showed entropically driven self-assembly and micellar nanostructures (nanoassemblies), which can sequester hydrophobic drug molecules at neutral pH. To further stabilize the nanoassemblies and the sequestered drug molecules even below its critical aggregation concentration (CAC), the micellar core was cross-linked via the thiol-acrylate Michael addition click reaction to generate multiple copies of acid labile β-thioester functionalities in the core, which undergo slow hydrolysis at endosomal pH (∼5.0), thus enabling sustained release of the anti-cancer drug doxorubicin at endosomal pH. The nanonetworks showed a significant decrease in drug leakage compared to the nanoassemblies (NAs), which was also justified by a low leakage coefficient calculated from the fluorescence resonance energy transfer experiment. The NN also exhibited dilution insensitivity and high serum stability, whereas the NA disassembled upon dilution and during serum treatment. The biological evaluation revealed tumor extracellular matrix pH (∼6.4-6.8) induced surface charge modulation and cancer cell (HeLa) selective activated cellular uptake of the doxorubicin loaded nanonetwork (NN-DOX). In contrast, the benign nature of NN-DOX towards normal cells (H9c2) suggests excellent cell specificity. Thus, we believe that the ease of synthesis, nanonetwork fabrication reproducibility, robust stability, smart nature of tumor microenvironment sensitive surface charge modulation, boosted tumoral-cell uptake, and triggered drug release will make this system a potential nanomedicine for chemotherapeutic treatments.

Melt Polycondensation Strategy for Amide-Functionalized l-Aspartic Acid Amphiphilic Polyester Nano-assemblies and Enzyme-Responsive Drug Delivery in Cancer Cells

Aliphatic polyesters are intrinsically enzymatic-biodegradable, and there is ever-increasing demand for safe and smart next-generation biomaterials including drug delivery nano-vectors in cancer research. Using bioresource-based biodegradable polyesters is one of the elegant strategies to meet this requirement; here, we report an l-amino acid-based amide-functionalized polyester platform and explore their lysosomal enzymatic biodegradation aspects to administrate anticancer drugs in cancer cells. l-Aspartic acid was chosen and different amide-side chain-functionalized di-ester monomers were tailor-made having aromatic, aliphatic, and bio-source pendant units. Under solvent-free melt polycondensation methodology; these monomers underwent polymerization to yield high molecular weight polyesters with tunable thermal properties. PEGylated l-aspartic monomer was designed to make thermo-responsive amphiphilic polyesters. This amphiphilic polyester was self-assembled into a 140 ± 10 nm-sized spherical nanoparticle in aqueous medium, which exhibited lower critical solution temperature at 40-42 °C. The polyester nano-assemblies showed excellent encapsulation capabilities for anticancer drug doxorubicin (DOX), anti-inflammatory drug curcumin, biomarkers such as rose bengal (RB), and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt. The amphiphilic polyester NP was found to be very stable under extracellular conditions and underwent degradation upon exposure to horse liver esterase enzyme in phosphate-buffered saline at 37 °C to release 90% of the loaded cargoes. Cytotoxicity studies in breast cancer MCF 7 and wild-type mouse embryonic fibroblasts cell lines revealed that the amphiphilic polyester was non-toxic to cell lines up to 100 μg/mL, while their drug-loaded polyester nanoparticles were able to inhibit the cancerous cell growth. Temperature-dependent cellular uptake studies further confirmed the energy-dependent endocytosis of polymer NPs across the cellular membranes. Confocal laser scanning microscopy assisted time-dependent cellular uptake analysis directly evident for the endocytosis of DOX loaded polymer NP and their internalization for biodegradation. In a nutshell, the present investigation opens up an avenue for the l-amino acid-based biodegradable polyesters from l-aspartic acids, and the proof of concept is demonstrated for drug delivery in the cancer cell line.

Development of Polyurethane/Peptide-Based Carriers with Self-Healing Properties

In situ-forming gels with self-assembling and self-healing properties are materials of high interest for various biomedical applications, especially for drug delivery systems and tissue regeneration. The main goal of this research was the development of an innovative gel carrier based on dynamic inter- and intramolecular interactions between amphiphilic polyurethane and peptide structures. The polyurethane architecture was adapted to achieve the desired amphiphilicity for self-assembly into an aqueous solution and to facilitate an array of connections with peptides through physical interactions, such as hydrophobic interactions, dipole-dipole, electrostatic, π–π stacking, or hydrogen bonds. The mechanism of the gelation process and the macromolecular conformation in water were evaluated with DLS, ATR-FTIR, and rheological measurements at room and body temperatures. The DLS measurements revealed a bimodal distribution of small (~30–40 nm) and large (~300–400 nm) hydrodynamic diameters of micelles/aggregates at 25 °C for all samples. The increase in the peptide content led to a monomodal distribution of the peaks at 37 °C (~25 nm for the sample with the highest content of peptide). The sol–gel transition occurs very quickly for all samples (within 20–30 s), but the equilibrium state of the gel structure is reached after 1 h in absence of peptide and required more time as the content of peptide increases. Moreover, this system presented self-healing properties, as was revealed by rheological measurements. In the presence of peptide, the structure recovery after each cycle of deformation is a time-dependent process, the recovery is complete after about 300 s. Thus, the addition of the peptide enhanced the polymer chain entanglement through intermolecular interactions, leading to the preparation of a well-defined gel carrier. Undoubtedly, this type of polyurethane/peptide-based carrier, displaying a sol–gel transition at a biologically relevant temperature and enhanced viscoelastic properties, is of great interest in the development of medical devices for minimally invasive procedures or precision medicine.

Tyrosine-Derived Polymers as Potential Biomaterials: Synthesis Strategies, Properties, and Applications

Peptide-based polymers are evolving as promising materials for various biomedical applications. Among peptide-based polymers, polytyrosine (PTyr)-based and l-tyrosine (Tyr)-derived polymers are unique, due to their excellent biocompatibility, degradability, and functional as well as engineering properties. To date, different polymerization techniques (ring-opening polymerization, enzymatic polymerization, condensation polymerization, solution-interfacial polymerization, and electropolymerization) have been used to synthesize various PTyr-based and Tyr-derived polymers. Even though the synthesis starts from Tyr, different synthesis routes yield different polymers (polypeptides, polyarylates, polyurethanes, polycarbonates, polyiminocarbonate, and polyphosphates) with unique functional characteristics, and these polymers have been successfully used for various biomedical applications in the past decades. This Review comprehensively describes the synthesis approaches, classification, and properties of various PTyr-based and Tyr-derived polymers employed in drug delivery, tissue engineering, and biosensing applications.

l-Amino Acid Based Phenol- and Catechol-Functionalized Poly(ester-urethane)s for Aromatic π-Interaction Driven Drug Stabilization and Their Enzyme-Responsive Delivery in Cancer Cells

Exploiting aromatic π-interaction for the stabilization of polyaromatic anticancer drugs at the core of the polymer nanoassemblies is an elegant approach for drug delivery in cancer research. To demonstrate this concept, here we report one of the first attempts on enzyme-responsive polymers from aryl-unit containing amino acid bioresources such as l-tyrosine and 3,4-dihydroxy-l-phenylalanine (l-DOPA). A silyl ether protection strategy was adopted to make melt polymerizable monomers, which were subjected to solvent free melt polycondensation to produce silyl-protected poly(ester-urethane)s. Postpolymerization deprotection yielded phenol- and catechol-functionalized poly(ester-urethane)s with appropriate amphiphilicity and produced 100 ± 10 nm size nanoparticles in an aqueous solution. The aromatic π-core in the nanoparticle turns out to be the main driving force for the successful encapsulation of anticancer drugs such as doxorubicin (DOX) and topotecan (TPT). The electron-rich catechol aromatic unit in l-DOPA was found to be unique in stabilizing the DOX and TPT, whereas its l-tyrosine counterpart was found to exhibit limited success. Aromatic π-interactions between l-DOPA and anticancer drug molecules were established by probing the fluorescence characteristics of the drug-polymer chain interactions. Lysosomal enzymatic biodegradation of the poly(ester-urethane) backbone disassembled the nanoparticles and released the loaded drugs at the cellular level. The nascent polymer was nontoxic in breast cancer (MCF7) and WT-MEF cell lines, whereas its DOX and TPT loaded nanoparticles showed remarkable cell growth inhibition. A LysoTracker-assisted confocal microscopic imaging study directly evidenced the polymer nanoparticles' biodegradation at the intracellular level. The present investigation gives an opportunity to design aromatic π-interaction driven drug stabilization in l-amino acid based polymer nanocarriers for drug delivery applications.

Degradable polyprodrugs: design and therapeutic efficiency

Prodrugs are developed to increase the therapeutic properties of drugs and reduce their side effects. Polyprodrugs emerged as highly efficient prodrugs produced by the polymerization of one or several drug monomers. Polyprodrugs can be gradually degraded to release therapeutic agents. The complete degradation of polyprodrugs is an important factor to guarantee the successful disposal of the drug delivery system from the body. The degradation of polyprodrugs and release rate of the drugs can be controlled by the type of covalent bonds linking the monomer drug units in the polymer structure. Therefore, various types of polyprodrugs have been developed based on polyesters, polyanhydrides, polycarbonates, polyurethanes, polyamides, polyketals, polymetallodrugs, polyphosphazenes, and polyimines. Furthermore, the presence of stimuli-responsive groups, such as redox-responsive linkages (disulfide, boronate ester, metal-complex, and oxalate), pH-responsive linkages (ester, imine, hydrazone, acetal, orthoester, P-O and P-N), light-responsive (metal-complex, o-nitrophenyl groups) and enzyme-responsive linkages (ester, peptides) allow for a selective degradation of the polymer backbone in targeted tumors. We envision that new strategies providing a more efficient synergistic therapy will be developed by combining polyprodrugs with gene delivery segments and targeting moieties.

Construction of esterase-responsive hyperbranched polyprodrug micelles and their antitumor activity in vitro

This research constructs an esterase-responsive hyperbranched polyprodrug nano pharmaceutical and investigates their antitumor activity. Polyprodrug micelle was prepared by one-pot method based on glutathione (GSH), doxorubicin (DOX), and polyethylene glycol (PEG) under the catalyst of N,N-dicyclohexylcarbodiimide (DCC), 4-dimethylaminopyridine (DMAP), and 1-hydroxybenzotriazole (HOBt). The polyprodrug was characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectrometer (FT-IR), ultraviolet-visible spectrophotometer (UV-Vis), dynamic light scattering (DLS), and transmission electron microscope (TEM), respectively. The antitumor activity of polyprodrug micelle was evaluated by Hela cell and the distributions of micelles in cells were observed by fluorescent microscope. The NMR and FT-IR confirmed that the DOX-GSH-PEG polyprodrug was successfully synthesized. The drug loading rate is 10.21% and particle size is 106.4 ± 1 nm with a narrowed polydispersity (PDI = 0.145). The DLS showed that the micelles were stable during 7 days at 25°C. The drug release results showed that the micelles could be esterase-responsive disrupted, and the drug release rate could reach 43% during 72 h. Cell uptake and cell viability demonstrated that the micelles could distribute to cell nuclei during 8 h and induce cell apoptosis during 48 h. Overall, these hyperbranched polyprodrug micelles prepared by one-pot method could be esterase-responsive disrupted and release the antitumor drugs in a high esterase environment for cancer therapy in vitro. These results confirm that DOX-GSH-PEG is an effective nanomedicine in vitro and the endogenous-based strategy with one-pot synthesis to construct esterase-responsive polyprodrug would probably be a preferred choice in the future.

Amino acid derived biopolymers: Recent advances and biomedical applications

Over the past few years, amino acids (AA) have emerged as promising biomaterials for the synthesis of functional polymers. Owing to the diversity of functional groups in amino acids, various polymerization methods may be used to make a wide range of well-defined functional amino-acid/peptide-based optically active polymers with varying polymer lengths, compositions, and designs. When incorporated with chirality and self-assembly, they offer a wide range of applications and are particularly appealing in the field of drug delivery, tissue engineering, and biosensing. There are several classes of these polymers that include polyamides (PA), polyesters (PE), poly(ester-amide)s (PEA)s, polyurethanes (PU)s, poly(depsipeptide)s (PDP)s, etc. They offer the ability to control functionality, conjugation, crosslinking, stimuli responsiveness, and tuneable mechanical/thermal properties. In this review, we present the recent advancements in the synthesis strategies for obtaining these amino acid-derived bio-macromolecules, their self-assembly properties, and the wealth of prevalent applications.

Tyrosol Derived Poly(ester-arylate)s for Sustained Drug Delivery from Microparticles

New biodegradable polymers are needed for use in drug delivery systems to overcome the high burst release, lack of sustained drug release, and acidic degradation products frequently observed in current formulations. Commercially available poly(lactide-co-glycolide) (PLGA) is often used for particle drug release formulations; however, it is often limited by its large burst release and acidic degradation products. Therefore, a biocompatible and biodegradable tyrosol-derived poly(ester-arylate) library has been used to prepare a microparticle drug delivery system which shows sustained delivery of hydrophobic drugs. Studies were performed using polymers with varying hydrophilicity and thermal properties and compared to PLGA. Various drug solubilizing cosolvents were used to load model drugs curcumin, dexamethasone, nicotinamide, and acyclovir. Hydrophobic drugs curcumin and dexamethasone were successfully loaded up to 50 weight percent (wt %), and a linear correlation between drug wt % loaded and the particle glass transition temperature (T_g) was observed. Both curcumin and dexamethasone were visible on the particle surface at 20 wt % loading and higher. By adjusting the polymer concentration during particle formation, release rates were able to be controlled. Release studies of dexamethasone loaded particles with a lower polymer concentration showed a biphasic release profile and complete release after 47 days. Particles prepared using a higher polymer concentration showed sustained release for up to 77 days. Comparably, PLGA showed a traditional triphasic release profile and complete release after 63 days. This novel tyrosol-derived poly(ester-arylate) library can be used to develop injectable, long-term release formulations capable of providing sustained drug delivery.

Biobased polyurethanes for biomedical applications

Polyurethanes (PUs) are a major family of polymers displaying a wide spectrum of physico-chemical, mechanical and structural properties for a large range of fields. They have shown suitable for biomedical applications and are used in this domain since decades. The current variety of biomass available has extended the diversity of starting materials for the elaboration of new biobased macromolecular architectures, allowing the development of biobased PUs with advanced properties such as controlled biotic and abiotic degradation. In this frame, new tunable biomedical devices have been successfully designed. PU structures with precise tissue biomimicking can be obtained and are adequate for adhesion, proliferation and differentiation of many cell's types. Moreover, new smart shape-memory PUs with adjustable shape-recovery properties have demonstrated promising results for biomedical applications such as wound healing. The fossil-based starting materials substitution for biomedical implants is slowly improving, nonetheless better renewable contents need to be achieved for most PUs to obtain biobased certifications. After a presentation of some PU generalities and an understanding of a biomaterial structure-biocompatibility relationship, recent developments of biobased PUs for non-implantable devices as well as short- and long-term implants are described in detail in this review and compared to more conventional PU structures.

Tumor Microenvironment-Stimuli Responsive Nanoparticles for Anticancer Therapy

Cancer is a disease that affects a large number of people all over the world. For treating cancer, nano-drug delivery system has been introduced recently with objective of increasing therapeutic efficiency of chemotherapeutic drug. The main characteristics of this system are the encapsulation of the insoluble chemotherapeutic cargo, increasing the period of circulation in the body, as well as the delivery of the drug at that specific site. Currently, the nano-drug delivery system based on the stimuli response is becoming more popular because of the extra features for controlling the drug release based on the internal atmosphere of cancer. This review provides a summary of different types of internal (pH, redox, enzyme, ROS, hypoxia) stimuli-responsive nanoparticle drug delivery systems as well as perspective for upcoming times.

Overcoming Biological Barriers With Block Copolymers-Based Self-Assembled Nanocarriers. Recent Advances in Delivery of Anticancer Therapeutics

Cancer is one of the most common life-threatening illness and it is the world's second largest cause of death. Chemotherapeutic anticancer drugs have many disadvantages, which led to the need to develop novel strategies to overcome these shortcomings. Moreover, tumors are heterogenous in nature and there are various biological barriers that assist in treatment reisistance. In this sense, nanotechnology has provided new strategies for delivery of anticancer therapeutics. Recently, delivery platforms for overcoming biological barriers raised by tumor cells and tumor-bearing hosts have been reported. Among them, amphiphilic block copolymers (ABC)-based self-assembled nanocarriers have attracted researchers worldwide owing to their unique properties. In this work, we addressed different biological barriers for effective cancer treatment along with several strategies to overcome them by using ABC-based self-assembled nanostructures, with special emphasis in those that have the ability to act as responsive nanocarriers to internal or external environmental clues to trigger release of the payload. These nanocarriers have shown promising properties to revolutionize cancer treatment and diagnosis, but there are still challenges for their successful translation to clinical applications.

Biodegradable Polymer Theranostic Fluorescent Nanoprobe for Direct Visualization and Quantitative Determination of Antimicrobial Activity

We report a biodegradable fluorescent theranostic nanoprobe design strategy for simultaneous visualization and quantitative determination of antibacterial activity for the treatment of bacterial infections. Cationic-charged polycaprolactone (PCL) was tailor-made through ring-opening polymerization methodology, and it was self-assembled into well-defined tiny 5.0 ± 0.1 nm aqueous nanoparticles (NPs) having a zeta potential of +45 mV. Excellent bactericidal activity at 10.0 ng/mL concentration was accomplished in Gram-negative bacterium Escherichia coli (E. coli) while maintaining their nonhemolytic nature in mice red blood cells (RBC) and their nontoxic trend in wild-type mouse embryonic fibroblast cells with a selectivity index of >10⁴. Electron microscopic studies are evident of the E. coli membrane disruption mechanism by the cationic NP with respect to their high selectivity for antibacterial activity. Anionic biomarker 8-hydroxy-pyrene-1,3,6-trisulfonic acid (HPTS) was loaded in the cationic PCL NP via electrostatic interaction to yield a new fluorescent theranostic nanoprobe to accomplish both therapeutics and diagnostics together in a single nanosystem. The theranostic NP was readily degradable by a bacteria-secreted lipase enzyme as well as by lysosomal esterase enzymes at the intracellular compartments in <12 h and support their suitability for biomedical application. In the absence of bactericidal activity, the theranostic nanoprobe functions exclusively as a biomarker to exhibit strong green-fluorescent signals in live E. coli. Once it became active, the theranostic probe induces membrane disruption on E. coli, which enabled the costaining of nuclei by red fluorescent propidium iodide. As a result, live and dead bacteria could be visualized via green and orange signals (merging of red+green), respectively, during the course of the antibacterial activity by the theranostic probe. This has enabled the development of a new image-based fluorescence assay to directly visualize and quantitatively estimate the real-time antibacterial activity. Time-dependent bactericidal activity was coupled with selective photoexcitation in a confocal microscope to demonstrate the proof-of-concept of the working principle of a theranostic probe in E. coli. This new theranostic nanoprobe creates a new platform for the simultaneous probing and treating of bacterial infections in a single nanodesign, which is very useful for a long-term impact in healthcare applications.

Programmed supramolecular nanoassemblies: enhanced serum stability and cell specific triggered release of anti-cancer drugs

A bolaamphiphilic cross-linked nanoassembly endowed with pH responsive degradation features has been designed and fabricated for stable noncovalent guest encapsulation and controlled release. The self-assembled bolaamphiphile is utilized to prepare cross-linked nanoassemblies to further stabilize the noncovalent guest encapsulation at a concentration below its critical aggregation concentration (CAC) in a large volume of water or serum for drug delivery applications. Thus, this system can simultaneously address premature drug release and safety issues. The nanoassemblies integrated with a β-thioester linker, which can be hydrolyzed selectively under mildly acidic conditions (pH ∼ 5.3) at a slow rate, thus enable controlled release of guest molecules. Biological evaluation revealed that doxorubicin loaded cross-linked nanoassemblies (CNs-DOX) are nontoxic to normal cells such as HEK-293 or PBMC, but in contrast, showed a robust apoptotic effect on colon cancer cells, HCT-116, indicating excellent specificity. Thus, the fabrication reproducibility, robust stability, triggered drug release and cell selective toxicity behavior make this small molecular system very promising in the field of chemotherapeutic applications.

Therapeutic polymeric nanomedicine: GSH-responsive release promotes drug release for cancer synergistic chemotherapy

To obtain an efficient dual-drug release and enhance therapeutic efficiency for combination chemotherapy, a glutathione (GSH)-responsive therapeutic amphiphilic polyprodrug copolymer (mPEG-b-PCPT) is synthesized to load doxorubicin (DOX) via hydrophobic and π–π stacking interaction. In this nanomedicine system (mPEG-b-PCPT/DOX), the ratio of the two drugs can be easily modulated by changing the loading content of DOX. The in vitro drug release curves and laser confocal images suggested that the release of CPT and DOX is induced through a “release promotes release strategy”: after internalization into tumor cells, the disulfide bonds in the nanomedicine are cleaved by glutathione (GSH) in the cytoplasm and then lead to the release of CPT. Meanwhile, the disassembly of nanomedicine immediately promotes the co-release of DOX. The optimum dose ratio of CPT and DOX is evaluated via the combination index (CI) value using HepG-2 cells. The results of cell apoptosis and cell viability prove the better synergistic efficiency of the nanomedicine than free drugs at the optimum dose ratio of 1. Consequently, this stimuli-responsive synergistic chemotherapy system provides a direction for the fabrication of nanomedicines possessing promising potential in clinical trials.

In the GSH-responsive doxorubicin loading camptothecin prodrug nanomedicine, easy modulation of the dose ratio and controlled co-release were achieved, and the synergistic effect was significantly improved.

Targeted Intracellular Delivery of Antibodies: The State of the Art

A dominant area of antibody research is the extension of the use of this mighty experimental and therapeutic tool for the specific detection of molecules for diagnostics, visualization, and activity blocking. Despite the ability to raise antibodies against different proteins, numerous applications of antibodies in basic research fields, clinical practice, and biotechnology are restricted to permeabilized cells or extracellular antigens, such as membrane or secreted proteins. With the exception of small groups of autoantibodies, natural antibodies to intracellular targets cannot be used within living cells. This excludes the scope of a major class of intracellular targets, including some infamous cancer-associated molecules. Some of these targets are still not druggable via small molecules because of large flat contact areas and the absence of deep hydrophobic pockets in which small molecules can insert and perturb their activity. Thus, the development of technologies for the targeted intracellular delivery of antibodies, their fragments, or antibody-like molecules is extremely important. Various strategies for intracellular targeting of antibodies via protein-transduction domains or their mimics, liposomes, polymer vesicles, and viral envelopes, are reviewed in this article. The pitfalls, challenges, and perspectives of these technologies are discussed.

Impact of Glycolipid Hydrophobic Chain Length and Headgroup Size on Self-Assembly and Hydrophobic Guest Release

Encapsulation of a hydrophobic guest molecule inside a micelle and its stimuli-sensitive release is a useful strategy for target-specific drug delivery. Herein, nine biobased glycolipids were derived from plant sources. The influence of headgroup on the stability and aggregation pattern in water with different alkyl chain lengths was investigated to deduce the structure-property relationship. External factors, such as temperature, pH, and NaCl and urea concentrations, were employed to explore stimuli response of glycolipid nanoassemblies. Furthermore, solvatochromic dyes, such as pyrene, N-phenyl-1-naphthylamine, and curcumin, were utilized to examine hydrophobe loading capacities of these glycolipid assemblies. A fluorescence study was performed to investigate the enzyme-sensitive hydrophobe release. Interestingly, the pH-sensitive hydrophobic guests showed pH-responsive release from dynamic micelles. Finally, the synthesized glycolipids revealed their nanoassemblies as smart carriers for hydrophobic cargo.

Biotin-Tagged Polysaccharide Vesicular Nanocarriers for Receptor-Mediated Anticancer Drug Delivery in Cancer Cells

Biotin-conjugated multistimuli-responsive polysaccharide vesicular nanocarriers are designed and developed, for the first time, to accomplish receptor-mediated endocytosis in cancer cells and to deliver anticancer drugs to intracellular compartments. For this purpose, a new renewable hydrophobic unit was custom designed with redox-degradable disulfide and enzyme-biodegradable aliphatic ester chemical linkages, and it was conjugated along with biotin on the dextran backbone. The dextran derivative self-assembled into nanovesicles of <200 nm in size, which were characterized by dynamic and static light scattering, electron, and atomic force microscopes. Avidin-HABA assay established the high affinity of biotin-tagged dextran vesicles toward membrane-receptors up to 25 nM concentration. Doxorubicin-hydrochloride (DOX.HCl)-loaded dextran vesicles exhibited stable formulation in phosphate-buffered saline (PBS) and fetal bovine serum (FBS). Redox-degradation by glutathione (GSH) showed 60% drug release, whereas lysosomal esterase enzyme enabled >98% drug release in 12 h. Confocal microscope and flow cytometry-assisted time-dependent cellular uptake studies revealed that the biotin-receptors overexpressed in cervical cancer cells (HeLa) exhibited larger drug accumulation through the receptor-assisted endocytosis process. This process enabled the delivery of higher amount of DOX and significantly enhanced the killing in cancer cells (HeLa) compared to wild-type mouse embryonic fibroblast cells (WT-MEF, normal cells). Control experiments such as biotin pretreatment in cancer cells and energy-suppressed cellular uptake at 4 °C further supported the occurrence of receptor-mediated endocytosis by the biotin-tagged polymer vesicles. This report provides first insights into the targeted polysaccharide vesicle platform, and the proof-of-concept is successfully demonstrated in biotin receptor-overexpressed cervical cancer cells.

Amino acid-derived stimuli-responsive polymers and their applications

The recent advances achieved in the study of various stimuli-responsive polymers derived from natural amino acids have been reviewed.

Recent Advances in Nanoparticle-Based Cancer Drug and Gene Delivery

Effective and safe delivery of anticancer agents is among the major challenges in cancer therapy. The majority of anticancer agents are toxic to normal cells, have poor bioavailability, and lack in vivo stability. Recent advancements in nanotechnology provide safe and efficient drug delivery systems for successful delivery of anticancer agents via nanoparticles. The physicochemical and functional properties of the nanoparticle vary for each of these anticancer agents, including chemotherapeutics, nucleic acid-based therapeutics, small molecule inhibitors, and photodynamic agents. The characteristics of the anticancer agents influence the design and development of nanoparticle carriers. This review focuses on strategies of nanoparticle-based drug delivery for various anticancer agents. Recent advancements in the field are also highlighted, with suitable examples from our own research efforts and from the literature.